Reversible printing method



March 15, 1966 R. 5. HAINES 3,240,932

REVERSIBLE PRINTING METHOD Filed 001;. 31, 1962 REVERSIBLE TRANSPARENT- TRANSLUCENT COAT/N6 OF A CONTINUOUS PHASE OF HIGH SOFTEN/NG POLYMER AND A MATERIAL DISPERSED THERE/N FROM THE GROUP OF ORTHO AND META B/PHENYL BENZENEROS/N, AB/ETIC ACID, PQLYMERIZED AB/ETIC ACID, HYDROGENATED AE/ETIC ACID, HYDROGENATED ROS/N, POL YMERIZED ROS/N, THE jgI/NgglgRiZH/Z/TOL ESTER 0F ROS/N AND THE PENTAERYTI-IR/TOL ESTER OF FIG.2

PRINT IN TRANSLUCENT COAT/N6 INVENTOR ROBERT 5. HAINES ATTORNEY PRINT IN TRANSPARENT COA TING United States Patent 3,240,932 REVERSIBLE PRINTING METHOD Robert S. Haines, Poughkeepsie, N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Oct. 31, 1962, Ser. No. 234,409 9 Claims. (Cl. 25049.5)

The present invention relates to reversible transparenttranslucent coatings and more particularly to a reversible printing method which is useful for infra-red and heat duplicating; pressure, heat and infra-red printing; and electron beam writing.

The method of this invention is of general utility as opposed to prior art recording, printing and duplicating procedures. There are a variety of thermo and light sensitive papers in present use for duplicating purposes. None of these papers, however, are reversible and therefore capable of being reused. Further, these papers are generally light deteriorating and must be accordingly given special care in storage both prior to their exposure and subsequent thereto. These papers are limited to heat or light energy duplicating which is the single purpose for which they were made.

Other recording procedures utilize static charge and heat to record on thermoplastic material. Developing of the recording by heat has to be done in a vacuum to prevent the thermoplastic film degradation. The care of the recorded surface is a major problem since the recording is on the surface of the thermoplastic. There is further a possibility of distortion of the recorded surface due to cold fiow. The recording cannot give positive or negative images when using a light source.

It is an object of the present invention to provide a reversible transparent-translucent coating having a wide variety of printing and duplicating uses.

-It is another object of the present invention to provide a reversible transparent-translucent coating which is responsive to heat, pressure and electron beams for producing graphic representations in its body.

It is another object of the present invention to provide a method for reversible printing which requires no special developing procedures.

It is a further object of the present invention to provide a reversible printing method for applying and removing graphic representations by forming transparent and translucent areas in a coating which are insensitive to light and normal temperature conditions.

It is a still further object of the present invention to provide an inexpensive method for printing and duplicating graphic representations in a coating which may be indefinitely stored without degradation or may be erased at will and the coating reused.

These and other objects are accomplished according to the broad aspects of the present invention by providing a reversible transparent-translucent coating supported on the flexible transparent backing and a method for reversible printing thereon. The reversible transparenttranslucent coating is composed of a high softening polymeric material and an easily stress micro-crystallizable low softening organic material dispersed or dissolved within the high softening material. Under normal as formed conditions the low softening material is in an amorphous state and the coating is transparent. The whole coating or predetermined areas of the coating may be stressed to cause the low softening material to crystallize. These microcrystallized areas give different optical transmission to light than areas in the coating which are not microcrystallized. These microcrystallized areas physically appear clouded or translucent rather than clear and transparent. When it is desired to erase the microcrystallized areas of the coating, an application of sufficient heat to 3,240,932 Patented Mar. 15, 1966 relieve the stresses within the coating is all that is necessary to revert the low softening material back to its original transparent amorphous state.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention as illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is an enlarged perspective view of the reversible fusion-microcrystalline sheet of the present invention;

FIGURE 2 is a perspective, schematic view of the reversible fusion-microcrystalline sheet having graphic representation applied according to one embodiment of the present invention; and

FIGURE 3 is a perspective, schematic view of the reversible fusion-microcrystalline sheet having a graphical representation made according to another embodiment of the present invention.

Referring now, more particularly, to FIGURE 1 therelow softening organic material in a high softening polymeric material. The high softening polymer and the low softening material must be compatible to give a transparent coating under the as formed condition.

The principal necessary characteristic of the low softening material is the ability to become microcrystallized and thereby affect optical light transmission through the coating under mechanical stresses. Further, these stresses must be able to be relieved and the material returned to its normal amorphous state by a simple annealing step within a relatively lOW temperature range such as from to 150 C. The low softening material also is completely compatible with the high softening material so that when it is in its amorphous state the reversible coating is fully transparent to light. The class of materials which exhibits such properties includes ortho and meta diphenyl benzene; wood rosin; certain difunctional rosin esters, such as the diglycerol or pentaerythritol esters of the rosin acid; polymerized rosin; hydrogenized rosin; abietic acid; esters of abietic acid and polymerized abietic acid. The esters of rosin acid and polymerized rosin are produced according to the teachings of United States Patent 2,263,915, issued to J. N. Borgein.

The high softening organic polymeric material may be any one of several plastic materials such as polyethylene terephthalate, polystyrene, styrene-acrylonitrile copolymers, polyvinylidene chloride and copolymers thereof with acrylonitrile, poly (methyl meth-acrylate), polyvinyl acetate, polyvinyl chloride and copolymers of polyvinyl chloride and polyvinyl acetate. The required conditions of the high softening material is that it is transparent to light, compatible with the low softening material and its softening point is at least 1030 C. above that of the low softening material in order that the coating will retain its shape during the fusion of the microcrystallized areas by heating.

A film of this matrix can be coated on any suitable transparent backing or support Web 12 such as polyethylene terephthalate, cellulose triacetate or cellulose diacetate film, or polycarbonate transparent film. The formulation for the coating may be coated on the backing or support by any of the diverse available coating procedures.

Where there are adhesion problems between the coating matrix and the backing web, a suitable adhesive precoating may be applied to the backing web prior to application of the coated film. The adhesive precoating should be incompatible with the coating to prevent the coatings from bleeding into one another. Examples of acceptable precoatings are 49000 Du Pont linear polyester resin (a trademark of the E. I. du Pont de Nemours Company) or a 35% acrylonitrile-65% butadiene copolymer.

A dye may be incorporated in the reversible coating or the precoating, or applied as a separate coating. The dye helps to provide contrast between the semi-opaque, microcrystalline and transparent, amorphous areas of the coating. Methylene blue and methyl violet are two of the wide choices of useful dyes which have been used.

The reversible transparent-translucent sheet is usable in two general reversible printing procedures. One is the stressing of the entire reversible sheet initially followed by the relieving of the strain in specific areas of the sheet to thereby represent graphic representations. The resulting product in this instance could take the form of FIGURE 2 wherein transparent graphic representations 14 are shown in a translucent coating 16. A method for straining the coating is to strain the coating by drawing the backing web side of the sheet over a smooth edge to cause the microcrystallization of the low softening material and the resultant translucent appearance of the entire sheet. The other procedure would be to initially form graphic representations in the sheet by straining specific areas in the shape of the desired representations. FIGURE 3 illustrates this product wherein a translucent representation 18 is present within the coating 20.

The duplication of printed material may be accomplished using the completely stressed translucent sheet. The translucent-transparent reversible sheet which has been stressed to its translucent condition is placed against the sheet of printed material and then irradiated from a heat source. Absorption of the radiation by the printed characters results in generation of heat which is then conducted through the coating. A heat pattern corresponding to the printed material is developed on the coating of suflicient intensity to relieve the stresses and crystallization in the coating and transparentize the coating in the areas corresponding to the printed matter. The duplicated printed matter appears as transparent areas in the generally translucent coating. The duplicated printed matter may be viewed as a positive or negative depending on the combination of transmitted and reflected light that it was viewed with. To erase the duplicated printed material from the coating, the film is passed under a heat irradiation source of high intensity or a black piece of paper is placed underneath the film and the pair passed under a less intense heat source. To duplicate other printed material on the same transparent-translucent coating the coated film is again strained and rerun under the heat irradiation source with another page of printed material. The reversible coating may thus be used indefinitely.

The other methods of using a completely stressed transparent-translucent reversible sheet are to strike the sheet with a heated striking instrument, to irradiate with heat through openings in type character insulated masks or grids, and to write on the surface by electron beam heating. In each case the heat must be applied for a sufficient time to allow the localized heated areas to increase in temperature sufficiently to bring the temperature of the microcrystallized low softening material above its softening point which causes the fusion of the crystals and thus transparentize these localized areas.

The unstrained film can be printed upon by application of force as by a stylus, compression die or by impact of a typewriter hammer. The application of force to the film induces strain and resultant microcrystallization of the low softening organic material in the film. The application of force is applied from the backing web side of the coated sheet. The surface of the striking instrument must be sufiiciently blunt so that the backing web is not injured by the strike. This procedure using the fusion-microcrystalline coating lends itself to a higher printing or typing speed than is obtained using a conventional typewriter or printer because there is no requirement to indent the material but only to strain it. The strained areas of the coating can be removed by heating the film or passing it through a heat source and reusing it again.

An electron beam can be used to apply microcrystallized images or other information on an unstrained coating. The electron beam must be of high voltage and a low current to effect the mechanical straining of the transparent-translucent coating. Erasure of the strained areas is accomplished by heating as in the previously described methods.

The following are examples of the present invention in detail. The examples are included merely to aid in the understanding of the invention and variations may be made by one skilled in the art without departing from the spirit and scope of this invention.

Example 1 The following mixture was ball milled overnight until a solution was obtained:

10 grams, 23% acrylonitrile, 77% styrene copolymer (Tyril 767, produced by Dow Chemical Co.)

6.7 grams, wood rosin (WW grade) 25.0 grams, toluene 25.0 grams, acetone The coating solution was deposited onto polyethylene terephthalate (Mylar produced by E. I. du Pont de Nemours and Company), polycarbonate and cellulose triacetate backing webs by means of a knife coater. The solvent was evaporated from the coating by flowing air over the coated sheets in a 130 F. oven. The dry film coating was transparent and approximately 0.5 mil in thickness. The coating on each of the backing webs was microcrystallized by drawing the backing web side of the film over a smooth edge. The appearance of strained film was translucent as compared to the transparent pre-stained film. A page of typewritten material was duplicated on the stressed sheet by passing the coated sheet in contact with the page of printed material under a heat radiation source. The printed material appeared in the coating as transparent areas while the remaining portions of the coating were translucent. The translucent areas in the coating were erased by passing the coating in contact with a black piece of paper under a heat radiation source.

Example 2 The following coating composition was brought into solution and applied to the three backing webs according to the procedure of Example 1:

10.0 grams, 20% acrylonitrile, 80% vinylidene chloride copolymer (Saran F--1000 cps.produced by Dow Chemical Co.)

6.7 grams, hydrogenated wood rosin (Staybelite resin produced by Hercules Powder Co.)

50.0 grams, methyl ethyl ketone The unstrained coating was transparent. A page of typewritten material was duplicated as described in Example 1. The printed material appeared in the coating as transparent areas while the remaining portions of the coating were translucent. The translucent areas of the coating were than erased by heating the coating to approximately C.

Example 3 The following coating composition was brought into solution and applied to the three backing webs according to the procedure of Example 1:

10.0 grams, 20% acrylonitrile, 80% vinylidene chloride (Saran F-120-1000 cps-produced by Dow Chemical Co.)

6.7 grams, wood rosin (FF grade) 50.0 grams, methyl ethyle ketone J The unstrained coating was transparent. A page of typewritten material was duplicated as described in Example 1. The printed material appeared in the coating as transparent areas while the remaining portions of the coating were translucent. The translucent areas of the coating were erased by heating the coating to approximately 150 C.

Example 4 A polyethylene terephthalate high softening resin was prepared by heating the following mixture with a nitrogen sparge for two hours at about 180 C. until the methyl alcohol had been completely removed from the reaction by the sparge:

Grams Dimethyl terephthalate 25.0 Dimethyl isophthalate 6.0 Ethylene glycol 18.0 Polyethylene glycol (400 molecular weight) 5.6 Calcium acetate 0.050 Antimony oxide (Sb O 0.016

Then the above mixture was further heated at 180 C. with agitation under a vacuum of 0.5 to 1.0 centimeter of mercury for a period of two hours. The resulting product being an isophthalate modified polyethylene terephthalate resin.

The polyethylene terephthalate resin together with the other following constituents in the proportions listed were brought into solution by ball milling overnight.

Grams Polyethylene terephthalate 10.0 Wood rosin (FF grade) 6.7 P-dioxane 50.0

Polyethylene terephthalate, polycarbonate and cellulose triacetate backing webs were coated by knife coating with the resulting coating solution. The solvent was evaporated by flowing air over the film in a 130 F. oven. The dry film coating was approximately 0.5 mil in thickness. Printed matter Was successively duplicated in the coating and erased as described in Example 1.

Example 5 The following materials were brought into solution in the following proportions and coated according to the procedure of Example 1:

10.0 grams, polyethylene, terephthalate (Polyester 1036 produced by the Goodyear Tire and Rubber Co.)

6.7 grams, wood rosin (FF grade) 50.0 grams, p-dioxane 0.2 grams, methyl violet The transparent coated films were struck from the backing side of the film with typewriter hammers from an ordinary typewriter. A separate sheet of plastic covered the hammers of the typewriter. The typewriter hammers induced microcrystallization in the coating where the hammer hit. In this manner, typed characters were printed in the coatings. Erasure was accomplished by application of high heat. Printed matter was also successively duplicated in the coating and erased as described in Example 1.

Example 6 The following materials were brought into solution in the following proportions and coated according to the procedure of Example 1:

10.0 grams, polyethylene terephthalate (Polyester 1036 produced by the Goodyear Tire and Rubber Co.)

6.7 grams, polymerized abietic acid (Dymerex produced by the Hercules Powder Co.)

50.0 grams, p-dioxane Printed matter was successfully duplicated in the coating and erased as described in Example 1. Microcrystallized areas were printed in the transparent coating by means of a typewriter as described in Example 5.

6 Example 7 The materials were brought into solution in the following proportions and coated according to the procedure of Example 1:

10.0 grams, polyethylene terephthalate (Polyester 1036 produced by the Goodyear Tire and Rubber Co.) 6.7 grams, pent-aerythritol ester of abietic acid (Pentalyn- A produced by Hercules Powder Co.) 50.0 grams, p-dioxane Printed matter was successively duplicated in the coating and erased as described in Example 1. Microcrystallized areas were printed in the transparent coating by means of a typewriter as described in Example 5.

Example 8 The following materials were polymerized for 24 hours within a closed jar in an oil bath maintained at 67 C.:

Grams Styrene monomer 100.0 Ortho diphenyl benzene 40.0 2,2-azobis-Z-methylpropionitrile 0.7

The Example 8 was repeated except that meta diphenyl benzene was substituted for the ortho diphenyl benzene in the following formulation:

Grams Styrene monomer 100.0 Meta diphenyl benzene 40.0 2,2 azobis-2 methylpropionitrile 0.7

Printed matter was successfully duplicated in the coating and erased as described in Example 1.

Examples 9-13 Polystyrene (Lusterx RLD-1-2020 produced by Bakelite Company, Union Carbide Corp), poly (methyl methacrylate) (Plexiglas produced by Rohm and Haas Co.), polyvinyl chloride (Geon X13 produced by B. F. Goodrich Chemical Co.), a copolymer of polyvinyl chloride (97%) and polyvinyl acetate (3%) (VYNW produced by Bakelite Co., Union Carbide Corp.), and a copolymer of polyvinyl chloride (87%) and polyvinyl acetate (13%) (VYHH produced by Bakelite Co., Union Carbide Corp.) were each brought into a tetrahydrofuran solution together with wood rosin (grade FF) according to the procedure of Example 1 and in the following proportions:

Grams Polymer 10.0 Wood rosin 6.7

Tetrahydrofuran 60.0

Each coating formulation was coated on polyethylene terephthalate and cellulose diacetate backing webs by a knife coater. The solvent was evaporated from the coating by flowing air over the coating in a F. oven. All coatings on the cellulose diacetate webs were uniform and transparent. The polystyrene and poly (methyl methacrylate) coating solution could not be made to adhere satisfactorily to the polyethylene terephthalate web. Printed matter was successfully duplicated in the coating and erased for each satisfactory coating as described in Example 1.

The proportion of the low softening material to the high softening material may be varied within limits depending largely on the coating composition used. Should too great a proportion of the low softening material be present in the coating, there would tend to be flaking from the surface of the coating of the crystallized low softening material. Further, the entire stability of the coating would be effected during heating for erasure of the translucent areas because of undue surface softening. Where too low a proportion of the low softening material is present there is, of course, the reduction in contrast between microcrystallized-translucent and the transparent areas of the coating.

The particular solvents and their proportions used in the examples such as toluene, acetone, methyl ethyl ketone and p-dioxane are merely exemplary. The function of the solvent in the formulation is to bring the high and low softening materials into solution and to serve as the vehicle for applying the desired coating to its backing. The solvent is not critical since it is evaporated during the drying of the coating. The amount of solvent is varied depending upon the desired viscosity of the coating solution. Coatings have been successfully made using a wide range of viscosities.

The coating thickness used throughout the examples was 0.5 mil dry film. Coatings have been prepared, however, where the dry film coating thickness ranged from 0.2 to 1.0 mil and the product was susceptible to the reversible printing method. Coatings of an even wider thickness range could no doubt be successfully used.

The invention thus provides the first truly reversible and reusable coating capable of being printed upon, and a reversible printing method to apply and erase graphic representations to and from the coating. The transpar ent coating may be stressed by a simple drawing of the supported coating over a smooth edge to cause microcrystallization within the coating and a resultant degree of opaqueness to the coating. This microcrystallization and opaqueness can then be removed by heating the coating to a temperature above the softening point of the microcrystallizing material in the coating and thereafter cooling the coating to room temperature. Both the stressing and the fusion of the microcrystallized coating may be done selectively. This results in the ability to print microcrystallized translucent or opaque areas on the transparent coating or to print transparent areas on the micro crystallized coating. The microcrystallized translucent or opaque areas are always capable of being reverted to their transparent condition by a simple heating of those areas of the coating.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is: 1. A reversible printing method, comprising: applying graphic representations by forming transparent and translucent stress micro-crystallized areas in a substrate supported coating;

said coating comprising a continuous phase of a high softening polymer, and a low softening resinous material dispersed within said continuous phase from the group consisting of ortho and meta biphenyl benzene, rosin, abietic acid, polymerized abietic acid, hydrogenated abietic acid, hydrogenated rosin, polymerized rosin, the pentaerythritol ester of rosin, and the pentaerythritol ester of abietic acid; said low softening material being compatible with said high softening polymer to the extent that the unstressed coating is substantially transparent; and said high softening polymer having a softening temperature at least 10 C. higher than said low softening material;

and removing said graphic representations by heating said coating to its transparent condition.

2. A reversible printing method, comprising:

applying a force against the substrate side of a transparent substrate-supported coating to cause the coating to become translucent in the localized areas in which said force was applied;

said coating comprising a continuous phase of a high softening polymer, and a low softening resinous material dispersed within said continuous phase from the group consisting of ortho and meta biphenyl benzene, rosin, abietic acid, polymerized abietic acid, hydrogenated abietic acid, hydrogenated rosin, polymerized rosin, the pentaerythritol ester of abietic acid; said low softening material being compatible with said high softening polymer to the extent that the unstressed coating is substantially transparent; and said high softening polymer having a softening temperature at leaest 10 C. higher than said low softening material;

and heating said coating to remove said translucent areas from said coating.

3. The method according to claim 2 wherein said force is a typewriter type hammer.

4. The method according to claim 2 wherein said force is a high voltage electron beam.

5. A reversible printing method, comprising:

drawing an already formed, normally transparent coating supported on a flexible, transparent base over a smooth edge to cause the coating to become uniformly micro-crystallized and translucent; said coating comprising a continuous phase of a high softening polymer, and a low softening resinous material dispersed within said continuous phase from the group consisting of ortho and meta biphenyl benzene, rosin, abietic acid, polymerized abietic acid, hydrogenated abietic acid, hydrogenated rosin, polymerized rosin, the pentaerythritol ester of rosin, and the pentaerythritol ester of abietic acid; said low softening material being compatible with said high softening polymer to the extent that the unstressed coating is substantially transparent; and said high softening polymer having a softening temperature at least 10 C. higher than said low softening material;

selectively heating said coating in the desired pattern until the microcrystallized portions of the coating heated are reverted to their normally transparent condition;

and heating said coating to remove said translucent areas from said coating.

6. The method of claim 5 wherein the said selective heating is accomplished using a heated striking instrument.

7. The method of claim 5 wherein said selective heating is accomplished by applying heat through openings in a heat insulated mask.

8. The method of claim 5 wherein the said selective heating is accomplished using a high current electron beam.

9. A method for duplicating graphic representations which are on a material that is relatively non-absorptive to radiant energy, comprising:

drawing an already formed coating supported on a flexible base over a smooth edge to cause the coating to change from its original transparent condition to a uniformly microcrystallized, translucent condition;

said coating comprising a continuous phase of a high softening polymer, and a low softening resinous material dispersed within said continuous phase from the group consisting of ortho and meta biphenyl benzene, rosin, abietic acid, polymerized abietic acid, hydrogenated abietic acid, hydrogenated rosin, polymerized rosin, the pentaerythritol ester of rosin,

9 1G and the pentaerythritol ester of abietic acid; said References Cited by the Examiner low softening material being compatible with said UNITED STATES PATENTS high softening polymer to the extent that the unstressed coating is substantially transparent; and said high softening polymer having a softening tempera- 2,269,038 1/1942 Perry. 5 2,346,670 4/1944 Engler et a1.

ture at least 10 C. higher than said low softening %We1g t-l material; ames e a. exposing the said coating While in contact with said 2,765,286 10/1956 Goldberg et 7 XR material having graphic representations thereon to 2,859,351 11/1958 Clark et -367 a source of radiant energy until a heat pattern corre- 10 2,979,974 2/1961 Alblls et 7 XR SPOnding to the said graphic representations i 1 3,025,180 3/1962 Dalton 117-36] veloped on said coating of sufficient intensity to 3,090,697 5/ 1963 Lawton et 1 117-36.7

relieve the stresses in the said coating and trans parentize the said coating in the areas corresponding WILLIAM MARTIN Pnmmy Examine"- to said graphic representations. 15 MURRAY KATZ, Examiner. 

1. A REVERSIBLE PRINTING METHOD, COMPRISING: APPLYING GRAPHIC REPRESENTATIONS BY FORMING TRANSPARENT AND TRANSLUCENT STRESS MICRO-CRYSTALLIZED AREAS IN A SUBSTRATE SUPPORTED COATING; SAID COATING COMPRISING A CONTINOUS PHASE OF A HIGH SOFTENING POLYMER, AND A LOW SOFTENIN RESINOUS MATERIAL DISPERSED WITHIN AID CONTINUOUS PHASE FROM THE GROUP CONSISTING OF ORTHO AND META BIPHENYL BENZENE, ROSIN, ABIETIC ACID, POLYMERIZED ABIETIC ACID, HYDROGENATED ABIETIC ACID, HYDROGENATED ROSIN, POLYMERIZED ROSIN, THE PENTAERYTHRITO ESTER OF ROSIN, AND THE PENTAERYTHRITOL ESTER OF ABIETIC ACID; SAID LOW SOFTENING MATERIAL BEING COMPATIBLE WITH SAID HIGH SOFTENING POLYMER TO THE EXTENT THAT THE UNSTRESSED COATING IS SUBSTANTIALLY TANPARENT; AND SAID HIGH SOFTENING POLYMER HAVING A SOFTENING TEMPERATURE AT LEAST 10*C. HIGHER THAN SAID LOW SOFTENING MATERIAL; AND REMOVING SAID RAPHIC REPRESENTATIONS BY HEATING SAID COATING TO ITS TRANSPARENT CONDITION. 